| 摘要 |
<p>A casting powder esp for molten steel is prepd. by (i) forming a mixt. of finely divided casting powder cpd(s). (esp. calcium aluminosilicate and/or carbon flyash) and pref. finely divided flux (esp. an alkaline cpd.); (ii) suspending the mixt. in a vehicle (esp. water); (iii) expanding the suspension (esp. by spraying or atomising) to form hollow spheroidal particles; and pref. (iv) calcining at above the m.pt. of the flux but below the softening pt. of the casting powder. Also claimed is a casting powder made as above and comprising hollow spheroidal particles of greater than 60 microns size, the individual particles contg. finely divided carbon of particle size pref. less than 20 microns, e.g. carbon black. The powder is homogeneous, ensuring uniform melting at the powder/molten steel interface, gives minimal dusting during use and, if calcined, has a short melting interval and contains combined silica (to prevent silicosis) and combined calcia (to prevent hygroscopicity). The presence of finely divided carbon in the particles of the casting powder gives a high surface tension to prevent premature melting of the casting powder and its combination with the molten steel at the powder/steel interface.</p> |
